The present invention relates to a power transmission system. The system of the present invention is particularly useful for bicycles, and is therefore described below with respect to this application.
The conventional power transmission system for bicycles includes a pair of foot pedals carried at the ends of a pair of crank arms and rotatable about a horizontal axis of the frame for rotating a chain wheel coupled by a chain to the rear wheel of the bicycle. One of the drawbacks in such a system is that it does not best exploit the power which a person can apply to the foot pedals. Thus, in the conventional bicycle the foot pedals are rigidly mounted 180.degree. apart, and the operator applies maxiumum power in the vertical downward strokes of the foot pedals. Minimum power is applied during the generally horizontal movements of the foot pedals, namely at the beginning and ends of the downwards strokes when the foot pedals are in or near their dead-center positions, i.e., in alignment with the bottom bracket axle. Since the two foot pedals are rigidly mounted 180.degree. apart, both reach this point of minimum power at the same time, thereby increasing the effort required by the operator to propel the bicycle.
An object of the present invention is to provide a novel power transmission system producing a more efficient transmission of power from a pair of crank arms to a driven wheel. A more particular object of the present invention is to provide a power transmission system especially useful for bicycles for providing a smoother, more uniform and more natural transmission of power from the bicycle foot pedals to the chain wheel of the bicycle, and thereby to the rear bicycle wheel.